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Determination of the amount of the amorphous phase using x-ray diffraction
Málek, Tomáš ; Daniš, Stanislav (advisor) ; Kužel, Radomír (referee)
Using quantitative analysis based on x-ray diffraction entails complication in the amorphous phase contribution to signal background which may affect results. Often it is impossible to ignore this contribution and thus is appropriately to use some method for separation of the amorphous phase contribution from signal eventually also determine amount of amorphous phase in the sample. Although x-ray diffraction is used for crystalline samples is almost inevitable keep sample clear from amorphous phase which is in all polycrystalline sample in some amount. In this thesis we will effort to determine method or combination of methods which is possible to use for determination of the amount of the amorphous phase that we can use for cleaning results of quantitative analysis from the amorphous phase contribution.
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Structure of submicrocrystalline materials studied by X-ray diffraction
Matěj, Zdeněk ; Kužel, Radomír (advisor) ; Lukáš, Petr (referee) ; Čerňanský, Marian (referee)
Structure of submicrocrystalline materials was investigated by X-ray powder diffraction, mainly by modelling of widths and shapes of diffraction profiles. The diffraction method was applied to colloid gold nanoparticles, copper samples deformed by equal channel angular pressing and titanium dioxide nanoparticles prepared by various chemical routes. Dislocations and twin faults were identified in the metallic samples from characteristic broadening of diffraction lines. Densities of lattice defects were estimated from the diffraction data. Possibilities and limits of the diffraction method for characterisation of a crystallite size distribution were tested on the titanium dioxide samples. Crystallites of size in the range 3-25 nm could be well characterised. The problems were encountered only for samples with extremely broad size dispersion. Diffraction methods and a computer program were developed and tested, which can be applied also for the analysis of thin films.
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Study of new type of Ti-NT nanotubes that can be used as a filler in polymer matrix
Brunátová, Tereza ; Kužel, Radomír (advisor) ; Valvoda, Václav (referee)
Title: Study of new type of Ti-NT nanotubes that can be used as a filler in polymer matrix Author: Tereza Brunátová Department: Department of Condensed Matter Physics Supervisor: doc. RNDr. Radomír Kužel, CSc. Abstract: The subject of presented work has been devoted to a structure of titanate nanotubes which were prepared by hydrothermal treatment of TiO2 powder in NaOH solution. Structure determination was done mainly with two complementary methods - X-ray diffraction and transmision elec- tron microscopy. A influence of structure by changing particle size and crystal structure of the initial powder TiO2 was studied as well. Three different mod- els of nanotube structure were build. These models were used for a calculation of powder X-ray diffraction pattern and they were compared to experiment pattern. Keywords: titanates nanotubes, computer simulations of powder X-ray diffrac- tion patterns, X-ray diffracion, electron microscopy
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Physical properties of ultrafine-grained polycrystals of magnesium based alloys
Vrátná, Jitka ; Janeček, Miloš (advisor) ; Kužel, Radomír (referee)
The objective of the thesis is the study of microstructure evolution, mechanical properties, defect structure and corrosion resistance of ultra-ne grained magnesium alloy AZ31 prepared by a combined two-step process: the extrusion and the equal-channel angular pressing (ECAP). The microstructure development was studied using light and transmission electron microscopy and electron backscatter diffraction (EBSD). Mechanical properties were studied by microhardness measurement and tensile tests and the defect structure by positron annihilation spectroscopy (PAS). The results of tensile tests indicates that the characteristic stress 0.2 increases slightly with increasing number of ECAP passes only to the second pass and then decreases signicantly with additional ECAP straining. This behaviour is in accordance with the results of PAS. EBSD measurements show that the microstructure of extruded and ECAPed material has a bimodal distribution of grain sizes. The bimodal distribution becomes homogeneous with increasing number of ECAP passes and no remaining large grains are observed after 8 passes. The average grain size in the specimen after 8 passes is in the submicrometer range and the fraction of high-angle grain boundary (HAGB) is approximately 80%. The extruded specimens after 8 ECAP passes show the best...
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